I was born in the town of Ryazan in the year 1849 into the family of a priest. I received my secondary education at the local theological seminary, which I recall with gratitude. We had a number of excellent teachers. One of them was the priest Feofilakt Antonovich Orlov,a man of lofty ideals. In general, in the seminary at that time (I do not know how it was afterwards), one could follow one's own intellectual inclinations, which was not the case, regrettably so, in the notorious Tolstoy gymnasiums (and, I think, also in the present ones).
One could lag in a given subject and get on in another, but this did not threaten one with trouble, including expulsion; as a matter of fact, it focused attention on one, and gave rise to speculation about the talents and abilities of the student in question. Influenced by literature of the sixties, and particularly by Pisarev, our intellectual interests turned to natural science; and many, myself included, decided to take this subject at the University.
In 1870, I entered the Petersburg University and studied in the natural history section of the physics and mathematics faculty. The faculty was in its heyday at the time. We had a number of professors with great names in science, men who were outstanding as lecturers.I chose animal physiology for my major course and took chemistry as a minor. Cyon tremendously impressed us physiologists.
We were fascinated by his ingeniously simple exposition of the most complex physiological questions and his skill in conducting experiments. One can never forget such a teacher. I did my first physiological work under his tuition.
In 1875, after obtaining the degree of Candidate of Natural Sciences, I enrolled in the third-year course of the Medico-Chirurgical Academy. I did so, not for the purpose of becoming a physician, but with the idea that after getting the degree of doctor of medicine, I would qualify for a chair in physiology. I must say, however, that at the time this plan seemed a vain dream because a professorship appeared as something unattainable, incredible.
When I entered the Academy, I was to become assistant to Prof. Cyon (he read lectures on physiology at this Academy too ) in place of S.I.. Chernov, who had to go abroad.
But an incredible thing happened : the brilliant physiologist was expelled from the Academy. After some time I obtained a position as assistant to Professor K. N. Ustimovich, lecturer on physiology at the Veterinary Institute. When Professor Ustimovich left the Institute - in 1878, I think.
Pavlov was seriously ill in 1927, 1935 and 1936. His illness could not be diagnosed correctly until April 1927. It was one of the worst fears come true, he was diagnosed as having - Cancer of liver. The most outstanding surgeons operated on him.
Pavlov was told to invite the best surgeons from Germany, but he refused saying that he did not consider the German surgeons better than Russians. His illness resulted in his death on February 17, 1936.
SEPTEMBER, 1849 Birth of Ivan Pavlov September 14, according to the Julian calendar, which was used in Russia up to 1917. September 27, according to the Gregorian calendar of Western Europe.
YEAR 1860 Ivan was unable to attend school, due to a childhood accident. At the age of 11, he joined a theological seminary.
YEAR 1863 He read J.M. Sechnow's book Reflexes of the Brain published the same year, which had an everlasting impression on his mind.
YEAR 1870
Inspired by Charles Darwin, he left the theological seminary and joined the University of St. Petersburg.
YEAR 1875 He graduated from the University of St. Petersbur
YEAR 1883 He received his doctorate in Medicine from the Military Medical Academy.
YEARS 1884 - 1886 Pavlov pursued further studies in Germany at Leipzig and Breslau.
YEARS 1888 - 1890 He investigated cardiac physiology and regulation of blood pressure. He became professor of physiology at the Military Medical Academy.
YEAR 1897 He pursued the study of gastrointestinal secretions in a normal animal. This work culminated in his book Lectures on the works of the Principal Digestive Glands.
YEAR 1903 Pavlov published his theory called Conditioned reflex.
YEAR 1904 He was awarded the Nobel Prize for his work in physiology of digestive glands.
YEAR 1924 He resigned from the Military Medical Academy as an Anti-Communal gesture.
YEAR 1930 He began his studies on human mental illness called neuroses and psychoses.
FEBRUARY 27, 1936 Pavlov died in Leningrad at the age of 87.
THE SIGNIFICANT OF HIS WORK
WORKS & EXPERIMENTS
Pavlov's first independent work was focused on the physiology of the circulation of blood. He studied the influence of variations in blood volume on blood pressure. The most important work performed during this period is incorporated in Pavlov's M.D. thesis, The Centrifugal Nerves of the Heart, which he presented to the Military Medical Academy in St. Petersburg in 1883. Four years later, this was published in the Archiv fur Physiologie under the title Uber die centrifugalen Nerven des Herzens.
The main conclusion from these investigations was that different fibres of the cardiac nerves control the rhythm and the strength of the contractions of the heart. According to Pavlov, the heart is supplied by four kinds of nerves :
(1) those which inhibit and (2) those which weaken its contractions, both reaching the heart along with the vagus nerve; (3) those which accelerate; and (4) those which augment them. The latter two nerves are derived from the sympathetic nervous system. The general opinion was, and still is, that there are only two nerves- vagus and sympathetic - which produce all the other effects on the heart.
From his experiments he concluded that the vagus nerve does not produce parallel double effects on the rhythm and the strength of cardiac contractions, but that these are two separate functions of the nerves, which are conveyed to the heart through different nerve fibres.
It was during this study that Pavlov experimented on un-anaesthetized, neurologically intact dogs. This method became the mainstay of Pavlov's methodology, which involved training dogs to lie calmly on the operating table while he incised the skin and surface tissue, exposed the artery and connected it to instruments for measuring blood pressure.
Pavlov felt that the experimental methods used by many researchers introduced too many sources of error. In order to understand the true physiological mechanisms of an organ, that organ had to be observed as it functioned as a part of a whole body, and not by itself.
Pavlov's second independent work (1890-1900) centered around the secretory activity of digestion. While working with Heidenhain, he devised an operation to prepare a miniature stomach or pouch. He isolated the stomach from ingested foods while preserving its vagal nerve supply. This surgical procedure helped him to study the gastrointestinal secretions in a normal animal over its life span.
Pavlov's accomplishments from the study of digestive organs included br />
O discovery of enterokinase, an enzyme in the duodenum that activates trypsin;
O description of the neural control of the pancreas and pancreatic control as a response to different foods;
O demonstration that chewing and swallowing alone would cause gastric secretion;
O conclusion that the secretory nerve that controls the gastric glands is the vagus nerve;
O demonstration of variance in types and amounts of secretions of the stomach in response to different foods;
O observation that the mere sight of food stimulates salivary and gastric secretion.
Pavlov published his results in a book called Lectures on the works of the Principal Digestive Glands, in 1897.He was awarded the Nobel Prize for this pioneering work and he happened to be the first Physiologist and first Russian to receive such a high honor.
THE EFFECT OF PAVLOV'S WORK ON PRESENT DAY LIFE
Before the appearance of Pavlov's Lectures, only a few physiologists knew his name outside Russia. The extraordinary success of his 'Lectures' was undoubtedly due to an unexpected revelation in them of a large number of new and striking facts and to the description of starting new physiological methods. Some of the facts had never been published before, however, these are not the reasons why his works aroused universal interest. Besides the factual material presented in the Lectures, it was for the first time in the history of gastroenterology that a comprehensive and coherent picture of the secretory activity of the alimentary canal as a whole, instead of a separate, unrelated but important facts was given.
After 1898, i.e. after the German translation of his book appeared, every physiologist and clinician based his study of the normal or abnormal physiology of the alimentary canal on Pavlov's Lectures.
It would not be an exaggeration to say that the facts discovered by Pavlov and his ideas became the foundation of modern gastroenterology.
THEORY OF CONDITIONED REFLEX
AN INTRODUCTION
Pavlov formulated the laws of conditioned reflex, by observing the irregularities of secretions in normal animals. He worked on this subject approximately from 1898 to 1930. The salivary secretion was used as a quantitative measure of the physical or subjective activity of the animal, so that the objective, psychological measures of the mental phenomena could be emphasized. He sought analogies between the Conditional reflex and the Spinal reflex. The spinal reflex, according to the physiologist Sir Charles Sherrington, is made up of the integrated actions of the nervous system involving complex components of nerves, and the irradiation of nerve impulses to the many nerve centers. Pavlov added cortical and sub cortical influences to these components, and the origin of neurotic disturbances due to collision or conflict between cortical excitation and inhibition.
Pavlov tried to apply his laws to the explanation of human psychoses in 1930. It was assumed that the excessive inhibition of a psychotic person was a protective mechanism. This idea became the basis for treating psychiatric patients. Pavlov announced that the important principle of language function in humans is based on long chain of conditioned reflexes.
THEORY OF CONDITIONED REFLEX
He studied the digestive process in dogs, especially the interaction between salivation and action of the stomach. He then realized that reflexes in the autonomic nervous system were closely linked to salivation and the process of digestion.
Therefore he experimented on hungry dogs. He trained hungry dogs to salivate at the sound of a bell. So he rang a bell and at the same time gave food to the experimental dogs. The dogs, which were already salivating, ate food as soon as they saw it.
As a result of this experiment, the dogs would start salivating immediately after they heard the bell ringing, even if there was no food available. He did so because he thought that without salivation, the stomach did not get the message to start digestion. In 1903, Pavlov published his results calling it a Conditioned Reflex, which is different from that of the usual reflex action like pulling away the organ from the source of pain. He called this learning process (for example, dog's nervous system comes to associate food with the sound of a bell) 'conditioning'. Further he found that the conditioned reflex would be repressed if the stimulus proves 'wrong' too often. The dog would stop salivating if there was no food, when the bell rang.
It is the same principle that makes our mouths water and stomachs awaken, when the aroma of food from a restaurant.
CLASSICAL CONDITIONING
CLASSICAL CONDITIONING :
A basic form of learning, in which, one stimulus serves as a signal for the occurrence of a second stimulus. During classical conditioning, organisms acquire information relating to various stimuli, not mere associations between them.
Unconditioned Stimulus (US)
In classical conditioning, a stimulus that elicits an unconditioned response the first time it is presented.
Unconditioned Response (UR)
It is the response elicited by an unconditioned stimulus.
Conditioned Stimulus (CS)
It is the stimulus that is repeatedly paired with an unconditioned stimulus.
Conditioned Response (CR)
In this case it is the response to the conditioned stimulus.
SYMBOLICALLY SHOWN AS :
US UR
(The original reflex the animal is born with).
CS - US UR
(Is followed by a repeated pairing of a stimulus (CS) with the reflex).
CS CR
(Which leads to an association between the new stimulus (CS) and the original response (UR), now called the (CR)).
CLASSICAL CONDITIONING PROCEDURE
The principles that govern the occurrence of classical conditioning :
Acquisition : The process by which a conditioned stimulus achieves the ability to elicit a conditioned response through repeated pairings of an unconditioned stimulus with the conditioned stimulus.
Delayed Conditioning : A type of forward conditioning in which the presentation of the conditioned stimulus precedes, but overlaps with, the presentation of the unconditioned stimulus.
Trace Conditioning : A form of forward conditioning in which presentation of the conditioned stimulus precedes but does not overlap with the presentation of the unconditioned stimulus.
Simultaneous Conditioning : A form of conditioning in which the conditioned stimulus and the unconditioned stimulus begin and end at the same time.
Backward Conditioning : A type of conditioning in which the presentation of the unconditioned stimulus precedes and does not overlap with the presentation of the conditioned stimulus.
Extinction : The process through which a conditioned stimulus gradually loses the ability to elicit conditioned responses when it is no longer followed by the unconditioned stimulus.
Reconditioning : The rapid recovery of a conditioned response upon reinstatement of Conditioned Stimulus - Unconditioned Stimulus pairings.
Spontaneous Recovery : After the process of extinction, return of a conditioned response upon reinstatement of Conditioned Stimulus - Unconditioned Stimulus pairings.
Stimulus Generalization : The tendency of stimuli similar to a conditioned stimulus elicits a conditioned response.
Stimulus Discrimination : The process by which organisms learn to respond to certain stimuli but not to others.
HIS LETTER TO THE YOUTH
What would I wish for the young people of my motherland who dedicated themselves to science ?
First of all - consistency of this very important condition for fruitful scientific work for which I cannot speak without emotion. Consistency, consistency and again consistency. Right from the very beginning, inculcate in yourself the habit of strict consistency in acquiring knowledge.
Learn the ABC of science before you attempt to scale its peaks. Never embark on what comes after without having mastered what goes before. Never try to cover up the gaps in your knowledge, even by the boldest of guesses and hypotheses. No matter how this bubble may delight the eye by its provision of colours, it is bound to burst, and you will be left with nothing but confusion.
Develop in yourself restraint and patience. Never funk the hard jobs in science. Study, compare, accumulate facts. No matter how perfect a bird's wing may be, it could never make the bird air-borne without the support of the air. Facts are the air of the scientist. Without them, you will never be able to take off; without them your ''theories" will be barren
But when studying, experimenting and observing, do your best to get beneath the skin of the facts. Do not become boarders of the facts. Try to penetrate into the secrets of their origin. Search persistently for the laws governing them.The second thing is modesty. Never think that you know everything. No matter in what high esteem you are held, always have the courage to say to yourself : ''I am ignorant."
Do not let pride take possession of you. It will result in you being obstinate when you should be conciliatory. It will lead you to reject useful advice and friendly help. It will deprive you of the ability to be objective.In the team which I am leader, everything depends on the atmosphere. All of us are harnessed to a common cause; and each pulls his weight. With us it is often impossible to discern what is ''mine" and what is ''yours", but our common cause only gains thereby.
The third thing is passion. Remember, science requires your whole life. And even if you had two lives to give, they would not be enough. Science demands of man the utmost effort and supreme passion. Be passionate in your work and in your quests.
Our country is opening wide vistas before scientists, and - it must be owned - science in our country is being pestered with a generous hand.What is there to say about the status of our young scientist ? Here, it would seem, everything is quite clear. Much is given to him, much is expected from him. For him, as for us, it is a matter of honor to justify the great trust that our country puts in science.
OPPOSITION TO COMMUNISM
Pavlov's relations with the communist Soviet Government were unique. He spoke fearlessly for what he considered the truth, eventhough he was not a politician. In 1922, he told Vladimir Lenin to transfer his laboratory abroad.
Lenin refused saying that Russia also needed scientists and wanted to give the facility of food rations only to Pavlov. He refused to accept such privileges unless his colleagues were given such rights. After returning from the United States, he denounced Communism.
He also resigned from the Military Medical Academy of Leningrad. In 1920, as an anticommunist gesture, he refused to allow Nikolay Bukharin, the Soviet commissioner of education, to enter his laboratory.
Though during the last two years of his life, he became more tolerant towards the government. The increased government support for science and the war with Japan brought about this change of heart.
• Pavlov had 10 siblings, 6 of whom died in childhood.
• So that they could condition the Russian population to celebrate Communism, the rulers in the new Soviet Union believed that they could take Pavlov's idea and apply it to develop a mass mind that applauds the communist way, rather than having people think critically for themselves.
• In 1904, the Nobel Prize consisted of 73,000 gold roubles, a very considerable sum in those days. Pavlov who had deposited the money in Nobels Russian firm, lost all of it, since Bolsheviks liquidated all the stocks and bonds of the firm during the Revolution of 1917.
• During Pavlov's visit to Stockholm, in the address which he gave as a recipient of a Nobel Prize he did not attempt to enlarge upon his achievements in the field of gastroenterology or to describe the investigations for which he was receiving the prize. On the contrary, he spoke at length about conditioned reflexes, which had just been discovered.
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